No service after lcd digitizer replacement!? (Tmobile)

Have fixed over 20 GS3s in my day, and this of course is my own personal one. After the screen was replaced, I only get service in WIFI areas. One/Zero bars everywhere else. Replaced sim card and even antennae. Still happening. I noticed a bit of water damage and scrubbed it. STILL didn't help. Any advice please? Maybe software? Or a chip may have broken off? Thanks in advance.

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